Multilayer interlayer having sound damping properties over a broad temperature range

ABSTRACT

A polymer interlayer having improved sound insulation is disclosed. The polymer interlayer comprises at least one soft layer wherein the soft layer comprises: a first poly(vinyl butyral) resin having a first residual hydroxyl content and a first glass transition temperature (T g ); a second poly(vinyl butyral) resin having a second residual hydroxyl content and a second glass transition temperature (T g ), wherein the difference between the first residual hydroxyl content and the second residual hydroxyl content is at least 1.0 weight percent; wherein the difference between the first glass transition temperature (T g ) the second glass transition temperature (T g ) is at least 1.5° C.; and a plasticizer; at least one stiffer layer comprising a third poly(vinyl butyral resin) having a third residual hydroxyl content; and a plasticizer, wherein the polymer interlayer has a damping loss factor (η) (as measured by Mechanical Impedance Measurement according to ISO 16940) of at least about 0.16 measured at two or more different temperatures selected from 10° C., 20° C. and 30° C.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This disclosure is related to the field of polymer interlayers formultiple layer glass panels and multiple layer glass panels having atleast one polymer interlayer sheet. Specifically, this disclosure isrelated to the field of acoustic polymer interlayers comprising multiplethermoplastic polymer layers.

2. Description of Related Art

Multiple layer panels are generally panels comprised of two sheets of asubstrate (such as, but not limited to, glass, polyester, polyacrylate,or polycarbonate) with one or more polymer interlayers sandwichedtherebetween. The laminated multiple layer glass panels are commonlyutilized in architectural window applications and in the windows ofmotor vehicles and airplanes. These applications are commonly referredto as laminated safety glass. Its main function is to absorb energy,such as that caused by a blow from an object, without allowingpenetration through the opening or the dispersion of shards of glass,thus minimizing damage or injury to the objects or persons within anenclosed area. Safety glass also can be used to provide other beneficialeffects, such as to attenuate acoustic noise, reduce UV and/or IR lighttransmission, and/or enhance the appearance and aesthetic appeal ofwindow openings.

The thermoplastic polymer found in safety glass can consist of a singlelayer of a thermoplastic polymer, such as poly(vinyl acetal) orpoly(vinyl butyral) (PVB), that has had one or more physicalcharacteristics modified in order to reduce the sound transmissionthrough the glass. Conventional attempts at such acoustic dampening haveincluded using thermoplastic polymers with low glass transitiontemperatures. Other attempts have included multilayer interlayers usingtwo adjacent layers of thermoplastic polymer wherein the layers havedissimilar characteristics (see, for example U.S. Pat. Nos. 5,340,654,5,190,826, and 7,510,771). These multilayer interlayers typicallycomprise a soft core layer having a single poly(vinyl acetal) resinhaving low residual hydroxyl content and two stiffer outer skin layerhaving a poly(vinyl acetal) resin having a significantly higher residualhydroxyl content. The soft core layer provides acoustic dampingproperties, while the stiff skin layers provide handling, processing andmechanical strength of the interlayer. The stiff outer layers generallycontribute very little to the acoustic damping properties.

The residual hydroxyl content in the core layer poly(vinyl acetal) resinand the amount of the plasticizer are optimized such that the interlayerprovides optimal sound insulation properties at ambient applicationtemperatures for multiple layer glass panels, such as windshields andwindows installed on vehicles and buildings. At temperatures above orbelow the ambient temperature, the sound insulation propertiesdeteriorate significantly. For example, if the tri-layer interlayercomposition is optimized such that the multiple layer glass panelcomprising the tri-layer interlayer has a maximum sound insulationperformance at 20° C. in its coincident frequency region (such as in theregion around 5,000 Hz), changing the application temperature by about10° C., such as decreasing the application temperature to 10° C. orincreasing the temperature to 30° C., the sound insulation significantlydecreases by several decibels or more. Further lowering or increasingthe temperature reduces the sound insulation performance even more.

Multiple layer glass panels produced with conventional multilayerinterlayers can have desirable sound insulation in one region of theworld, but they can have lower or mediocre sound insulation in otherregions of the world where the ambient temperatures differ. Even in thesame region, as the seasons change in a year, the sound insulationability of the glass panels also changes.

Accordingly, there is a need in the art for the development of amultilayer interlayer that has sound insulation performance over abroader temperature range. More specifically, there is a need in the artfor the development of multilayer interlayers having at least one softcore layer that provides sound insulation performance over a broadertemperature range.

SUMMARY OF THE INVENTION

Because of these and other problems in the art, described herein, amongother things are multilayered interlayers comprised of stiff skin layersand a soft core layer(s). In an embodiment, these multilayeredinterlayers comprise: a first polymer layer (skin layer) comprisingplasticized poly(vinyl butyral) resin; a second polymer layer (corelayer) comprising a blend of two or more plasticized poly(vinyl butyral)resins having different residual hydroxyl content; and a third polymerlayer (skin layer) comprising plasticized poly(vinyl butyral) resin. Thesecond polymer layer is disposed between the first polymer layer and thethird polymer layer, resulting in two skin layers and a central corelayer.

In an embodiment, a polymer interlayer having improved sound insulationis disclosed, the polymer interlayer comprising: at least one soft layerwherein the soft layer comprises: a first poly(vinyl butyral) resinhaving a first residual hydroxyl content and a first glass transitiontemperature (T_(g)); a second poly(vinyl butyral) resin having a secondresidual hydroxyl content and a second glass transition temperature(T_(g)), wherein the difference between the first residual hydroxylcontent and the second residual hydroxyl content is at least 1.0 weightpercent; wherein the difference between the first glass transitiontemperature (T_(g)) the second glass transition temperature (T_(g)) isat least 1.5° C.; and a plasticizer; at least one stiffer layercomprising a third poly(vinyl butyral resin) having a third residualhydroxyl content; and a plasticizer, wherein the polymer interlayer hasa damping loss factor (η) (as measured by Mechanical ImpedanceMeasurement according to ISO 16940) of at least about 0.16 measured attwo or more different temperatures selected from 10° C., 20° C. and 30°C.

In embodiments, the polymer interlayer has a damping loss factor (η) (asmeasured by Mechanical Impedance Measurement according to ISO 16940) ofat least about 0.17 measured at two or more different temperaturesselected from 10° C., 20° C. and 30° C., or at least about 0.18, or atleast about 0.19, or at least about 0.20, or at least about 0.21, or atleast about 0.22 or at least about 0.23 or at least about 0.24, or atleast about 0.25.

In embodiments, the second poly(vinyl butyral) resin is present in anamount of from about 5 weight percent to about 50 weight percent, orfrom about 25 weight percent to about 50 weight percent.

In embodiments, each plasticized resin in the soft layer of the polymerinterlayer has a glass transition temperature (T_(g)) less than 20.0°C., or less than 19.0° C., or less than 18.0° C., or less than 17.0° C.,or less than 16.0° C., or less than 15.0° C. In embodiments, thedifference between the glass transition temperatures (T_(g)) of thefirst poly(vinyl butyral) resin and the second poly(vinyl butyral) resinis at least 2.0° C., or at least 2.5° C., or at least 3.0° C., or atleast 4.0° C., at least 5.0° C.

In embodiments, the residual hydroxyl content of the third poly(vinylbutyral resin) is the same as the residual hydroxyl content of the firstpoly(vinyl butyral resin) or the second poly(vinyl butyral resin). Inembodiments, the difference between the first residual hydroxyl contentand the second residual hydroxyl content is at least 2.0 weight percent,or at least 3.0 weight percent, or at least 4.0 weight percent, or atleast 5.0 weight percent.

In another embodiment, a polymer interlayer having improved soundinsulation is disclosed, the polymer interlayer comprising: at least onesoft layer wherein the soft layer comprises: a first poly(vinyl butyral)resin having a first residual hydroxyl content and a first glasstransition temperature (T_(g)); a second poly(vinyl butyral) resinhaving a second residual hydroxyl content and a second glass transitiontemperature (T_(g)), wherein the difference between the first residualhydroxyl content and the second residual hydroxyl content is at least1.0 weight percent; wherein the difference between the first glasstransition temperature (T_(g)) the second glass transition temperature(T_(g)) is at least 1.5° C.; and a plasticizer; at least one stifferlayer comprising a third poly(vinyl butyral resin) having a thirdresidual hydroxyl content; and a plasticizer, wherein the polymerinterlayer has a damping loss factor (η) (as measured by MechanicalImpedance Measurement according to ISO 16940) of at least about 0.16measured at two or more different temperatures selected from 10° C., 20°C. and 30° C., and wherein the second poly(vinyl butyral) resin ispresent in an amount of from about 5 weight percent to about 50 weightpercent. In embodiments, the second poly(vinyl butyral) resin is presentin an amount of from about 25 weight percent to about 50 weight percent.

In embodiments, the polymer interlayer has a damping loss factor (η) (asmeasured by Mechanical Impedance Measurement according to ISO 16940) ofat least about 0.17 measured at two or more different temperaturesselected from 10° C., 20° C. and 30° C., or at least about 0.18, or atleast about 0.19, or at least about 0.20, or at least about 0.21, or atleast about 0.22 or at least about 0.23 or at least about 0.24, or atleast about 0.25.

In embodiments, each plasticized resin in the soft layer of the polymerinterlayer has a glass transition temperature (T_(g)) less than 20.0°C., or less than 19.0° C., or less than 18.0° C., or less than 17.0° C.,or less than 16.0° C., or less than 15.0° C. In embodiments, thedifference between the glass transition temperatures (T_(g)) of thefirst poly(vinyl butyral) resin and the second poly(vinyl butyral) resinis at least 2.0° C., or at least 2.5° C., or at least 3.0° C., or atleast 4.0° C., at least 5.0° C.

In embodiments, the residual hydroxyl content of the third poly(vinylbutyral resin) is the same as the residual hydroxyl content of the firstpoly(vinyl butyral resin) or the second poly(vinyl butyral resin). Inembodiments, the difference between the first residual hydroxyl contentand the second residual hydroxyl content is at least 2.0 weight percent,or at least 3.0 weight percent, or at least 4.0 weight percent, or atleast 5.0 weight percent.

In another embodiment, a polymer interlayer having improved soundinsulation is disclosed, the polymer interlayer comprising: at least onesoft layer wherein the soft layer comprises: a first poly(vinyl butyral)resin having a first residual hydroxyl content and a first glasstransition temperature (T_(g)); a second poly(vinyl butyral) resinhaving a second residual hydroxyl content and a second glass transitiontemperature (T_(g)), wherein the difference between the first residualhydroxyl content and the second residual hydroxyl content is at least1.0 weight percent, wherein the difference between the first glasstransition temperature (T_(g)) and the second glass transitiontemperature (T_(g)) is at least 1.5° C.; and a plasticizer; at least onestiffer layer comprising a third poly(vinyl butyral resin) having athird residual hydroxyl content; and a plasticizer, wherein eachplasticized resin in the soft layer of the polymer interlayer has aglass transition temperature (T_(g)) less than 20.0° C. In embodiments,each plasticized resin in the soft layer of the polymer interlayer has aglass transition temperature (T_(g)) less than 19.0° C., or less than18.0° C., or less than 17.0° C., or less than 16.0° C., or less than15.0° C.

In embodiments, the second poly(vinyl butyral) resin is present in anamount of from about 5 weight percent to about 50 weight percent, orfrom about 25 weight percent to about 50 weight percent.

In embodiments, the difference between the glass transition temperatures(T_(g)) of the first poly(vinyl butyral) resin and the second poly(vinylbutyral) resin is at least 2.0° C., or at least 2.5° C., or at least3.0° C., or at least 4.0° C., at least 5.0° C.

In embodiments, the residual hydroxyl content of the third poly(vinylbutyral resin) is the same as the residual hydroxyl content of the firstpoly(vinyl butyral resin) or the second poly(vinyl butyral resin). Inembodiments, the difference between the first residual hydroxyl contentand the second residual hydroxyl content is at least 2.0 weight percent,or at least 3.0 weight percent, or at least 4.0 weight percent, or atleast 5.0 weight percent.

In embodiments, the polymer interlayer has a damping loss factor (η) (asmeasured by Mechanical Impedance Measurement according to ISO 16940) ofat least about 0.16 measured at two or more different temperaturesselected from 10° C., 20° C. and 30° C., or at least about 0.17, or atleast about 0.18, or at least about 0.19, or at least about 0.20, or atleast about 0.21, or at least about 0.22 or at least about 0.23 or atleast about 0.24, or at least about 0.25.

A multiple layer panel is also disclosed. The multiple layer panelcomprises at least one rigid substrate, and a polymer interlayer ormultiple layer polymer interlayer as disclosed herein. The panel hasimproved sound insulation properties.

A method of making a polymer interlayer is also disclosed, wherein thepolymer interlayer has improved sound insulation, the polymer interlayercomprising: at least one soft layer wherein the soft layer comprises: afirst poly(vinyl butyral) resin having a first residual hydroxyl contentand a first glass transition temperature (T_(g)); a second poly(vinylbutyral) resin having a second residual hydroxyl content and a secondglass transition temperature (T_(g)), wherein the difference between thefirst residual hydroxyl content and the second residual hydroxyl contentis at least 1.0 weight percent; wherein the difference between the firstglass transition temperature (T_(g)) and the second glass transitiontemperature (T_(g)) is at least 1.5° C.; and a plasticizer; at least onestiffer layer comprising a third poly(vinyl butyral resin) having athird residual hydroxyl content; and a plasticizer, wherein the polymerinterlayer has a damping loss factor (η) (as measured by MechanicalImpedance Measurement according to ISO 16940) of at least about 0.16measured at two or more different temperatures selected from 10° C., 20°C. and 30° C., as disclosed herein.

A method of making a polymer interlayer is also disclosed, wherein thepolymer interlayer has improved sound insulation, the polymer interlayercomprising: at least one soft layer wherein the soft layer comprises: afirst poly(vinyl butyral) resin having a first residual hydroxyl contentand a first glass transition temperature (T_(g)); a second poly(vinylbutyral) resin having a second residual hydroxyl content and a secondglass transition temperature (T_(g)), wherein the difference between thefirst residual hydroxyl content and the second residual hydroxyl contentis at least 1.0 weight percent; wherein the difference between the firstglass transition temperature (T_(g)) the second glass transitiontemperature (T_(g)) is at least 1.5° C.; and a plasticizer; at least onestiffer layer comprising a third poly(vinyl butyral resin) having athird residual hydroxyl content; and a plasticizer, wherein the polymerinterlayer has a damping loss factor (η) (as measured by MechanicalImpedance Measurement according to ISO 16940) of at least about 0.16measured at two or more different temperatures selected from 10° C., 20°C. and 30° C., and wherein the second poly(vinyl butyral) resin ispresent in an amount of from about 5 weight percent to about 50 weightpercent. In embodiments, the second poly(vinyl butyral) resin is presentin an amount of from about 25 weight percent to about 50 weight percent,as disclosed herein.

A method of making a polymer interlayer is also disclosed, wherein thepolymer interlayer has improved sound insulation, the polymer interlayercomprising: at least one soft layer wherein the soft layer comprises: afirst poly(vinyl butyral) resin having a first residual hydroxyl contentand a first glass transition temperature (T_(g)); a second poly(vinylbutyral) resin having a second residual hydroxyl content and a secondglass transition temperature (T_(g)), wherein the difference between thefirst residual hydroxyl content and the second residual hydroxyl contentis at least 1.0 weight percent, wherein the difference between the firstglass transition temperature (T_(g)) and the second glass transitiontemperature (T_(g)) is at least 1.5° C.; and a plasticizer; at least onestiffer layer comprising a third poly(vinyl butyral resin) having athird residual hydroxyl content; and a plasticizer, wherein eachplasticized resin in the soft layer of the polymer interlayer has aglass transition temperature (T_(g)) less than 20.0° C., as disclosedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chart showing the damping loss factor at 10° C., 20° C., and30° C. for a disclosed interlayer (DI-5) and a comparative interlayer(CI-2).

FIG. 2 is a chart showing the damping loss factor at 10° C., 20° C., and30° C. for a disclosed interlayer (DI-14) and a comparative interlayer(CI-2).

FIG. 3 is a chart showing the damping loss factor at 10° C., 20° C., and30° C. for a disclosed interlayer (DI-24) and a comparative interlayer(CI-2).

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Described herein, among other things, are multilayer interlayers havingimproved sound insulation comprised of at least one soft core layercomprising a mixture of a first resin and a second resin, and at leastone stiff skin layer, wherein the residual hydroxyl content (measured as% PVOH by weight) in the second resin is higher than the residualhydroxyl content in the first resin. In some embodiments, the residualhydroxyl content in the second resin is lower than the residual hydroxylcontent in the skin layer(s). The first resin and second resin each havea glass transition temperature (T_(g)), and the glass transitiontemperatures of the first and second resins are different.

The inventor has surprisingly discovered that the sound insulationproperty of a multiple layer glass panel can be maintained over a broadtemperature range by incorporating a specific multilayer interlayer intothe glass panels. The multilayer interlayer has a soft core layer havingmore than one glass transition. By formulating the core layer in themultiple layer interlayer to have more than one glass transition, asfurther described herein, the sound insulation property of multiplelayer glass panels comprising the improved multiple layer interlayer canbe improved compared to glass panels comprising conventional multilayerinterlayers having a core layer with only a single glass transitiontemperature.

Further, because embodiments of the present invention having threepolymer layers (i.e., a tri-layer interlayer) can be formulated to beeasily handled and can be used as a direct replacement for conventionalinterlayers in conventional processes, these improved interlayers willbe usable in many applications without requiring any modification to thecurrent manufacturing methods. For example, automotive windshieldscomprising a conventional polymer interlayer can be replaced with aninterlayer of the present invention without altering the laminationprocess used to form the finished windshield.

As used herein, an “interlayer” is any thermoplastic construct that canbe used in multiple layer glass applications, such as safety glass inwindshields and architectural windows. The terms “multilayer” and“multiple layers” mean an interlayer having more than one layer, andmultilayer and multiple layer may be used interchangeably. Multilayerinterlayers typically contain at least one soft layer and at least onestiff layer.

In various embodiments of the present invention, a multiple layerinterlayer comprises two polymer layers disposed in contact with eachother, wherein one polymer layer is soft and the other polymer layer isstiff, and wherein each polymer layer comprises a thermoplastic polymerresin. The thermoplastic polymer can be the same or different in eachlayer.

Multiple layer glass panels having good sound insulation properties overa broad temperature range can be achieved by formulating the soft corelayer to exhibit multiple glass transition temperatures (T_(g)). Thesoft core layer is then combined with, such as laminated with, one ormore stiff layers to form a single, multilayer interlayer by theprocesses known in the arts, such as co-extrusion or lamination. Thesoft core layer having multiple glass transition temperatures comprisesa mixture of at least a first resin and a second resin, wherein the coreresins, either plasticized or unplasticized, each have a different glasstransition and glass transition temperature, wherein the glasstransition temperature in the second polymer resin differs from theglass transition temperature in the first polymer resin. Additionally,the glass transition in the second polymer resin is lower than the glasstransition temperature of the stiff skin or outer layer.

As used herein, the glass transition of a polymer is the state from the“glassy” state into the rubbery state, which is reversible; the glasstransition temperature is the temperature that marks the transition fromthe glassy state to the rubbery state. At the glass transition state,the polymer provides highest acoustic damping, and the glass transitiontemperature is used to characterize the acoustic insulation property ofthe polymer. The glass transition temperature (T_(g)) can be determinedby dynamic mechanical thermal analysis (DMTA). The DMTA measures thestorage (elastic) modulus (G′) in Pascals, loss (viscous) modulus (G″)in Pascals, tan delta (=G″/G′) of the specimen as a function oftemperature at a given frequency, and temperature sweep rate. Afrequency of 1 Hz and temperature sweep rate of 3° C./min were used. TheT_(g) is then determined by the position of the tan delta peak on thetemperature scale in ° C.

In various embodiments of present invention, at least one of the polymerlayers comprises a poly(vinyl acetal) resin, such as poly(vinylbutyral), and a plasticizer. In other embodiments, all polymer layerscomprise poly(vinyl acetal) resins or poly(vinyl butyral) resins andplasticizers. The soft core layer comprises a mixture of at least afirst resin having a first residual hydroxyl content and a second resinhaving a second residual hydroxyl content, wherein the residual hydroxylcontent (measured as % PVOH by weight) in the second resin differs fromthat in the first resin, and wherein the residual hydroxyl contents inboth the first and second resins are lower than the residual hydroxylcontent in the skin layer(s).

As used herein, residual hydroxyl content (calculated as % vinylhydroxyl content or poly(vinyl alcohol) (PVOH) by weight) in PVB refersto the amount of hydroxyl groups remaining on the polymer chains afterprocessing is complete. For example, PVB can be manufactured byhydrolyzing poly(vinyl acetate) to poly(vinyl alcohol (PVOH), and thenreacting the PVOH with butyraldehyde. In the process of hydrolyzing thepoly(vinyl acetate), typically not all of the acetate side groups areconverted to hydroxyl groups. Further, reaction with butyraldehydetypically will not result in all hydroxyl groups being converted toacetal groups. Consequently, in any finished PVB resin, there typicallywill be residual acetate groups (as vinyl acetate groups) and residualhydroxyl groups (as vinyl hydroxyl groups) as side groups on the polymerchain. As used herein, residual hydroxyl content and residual acetatecontent is measured on a weight percent basis per ASTM D1396.

In various embodiments, the first PVB resin in the softer core layer isselected, when plasticized, to have a glass transition temperature,T_(g1), and provide a sound insulation property at an applicationtemperature T1, and the second polymer resin having a different residualhydroxyl content is selected to have a glass transition temperature,T_(g2), and provide a sound insulation property at second applicationtemperature T2. More resins having different residual hydroxyl contentsthan the first and the second resins can also be selected and have glasstransition temperatures T_(g3), T_(g4), . . . T_(gn) (where n is thenumber of different resins), and incorporated into the core layer toprovide sound insulation properties at application temperatures T3, T4,. . . Tn (where n is the number of different resins), resulting in thecore layer having multiple glass transitions and exhibiting multipleglass transition temperatures T_(g1), T_(g2), T_(g3), T_(g4), . . .T_(gn), and providing sound insulation properties over a broadertemperature range.

Prior art attempts to produce multiple layer interlayers (comprising atleast two adjacent polymer layers) that reduce sound transmissionthrough a multiple layer glass panel have relied on variouscompositional permutations or differences between the two or morelayers. Conventional multiple layer interlayers have a core layer thathas a single resin and exhibits a single glass transition temperature.One prior art method teaches the use of acetals of differing carbonlength (see, for example, U.S. Pat. No. 5,190,826). Another prior artmethod teaches the use of differing polymerization degrees (see, forexample, Japanese Patent Application 3124441A or U.S. Patent Application2003/0139520 A1). Another method of varying the layers is the use of aPVB resin having residual acetate levels of at least 5 mole % in one oftwo adjacent layer as a compositional difference (see, for example,Japanese Patent 3,377,848 and U.S. Pat. No. 5,340,654). Finally, othermethods use poly(vinyl butyral) resins having different plasticizerconcentrations (see, for example, U.S. Pat. No. 7,510,771). All of theseinterlayers provide sound insulation properties only within a narrowtemperature range.

In various embodiments, the core layer comprises two poly(vinyl butyral)resins and a plasticizer. The second plasticized resin has a glasstransition temperature which differs by at least about 1.5° C. from thatof the first plasticized resin, or at least about 2° C., or at least2.5° C., or at least 3° C., or at least 4° C., or at least 5° C., or atleast 6° C., or at least 7° C., or at least 8° C., or at least 9° C., orat least 10° C., or at least 11° C., or by at least 12° C. or more. Thefirst plasticized resin can have a glass transition temperature from−40° C. to about 25° C., or about −30° C. to 20° C., or about −20° C. to10° C., or about 25° C. or less, or about 20° C. or less, or about 15°C. or less, or about 10° C. or less, or about 9° C. or less, or about 8°C. or less, or greater than about −40° C., or greater than about −35°C., or greater than about −30° C., or greater than about −25° C., orgreater than about −20° C. As used herein, the glass transitiontemperature of the plasticized resin is determined on the sheet formedby the individual plasticized resin, e.g., prior to mixing with anotherplasticized resin to form, for example, a core layer.

In various embodiments, the core layer comprises more than twopoly(vinyl butyral) resins and a plasticizer. The glass transitiontemperatures, T_(g1) T_(g2), T_(g3), . . . correspond to each of theplasticized resins and the difference in glass transition temperaturesof two adjacent plasticized resins is at least 1.5° C., or at least 1.6°C., or at least 1.7° C., or at least 1.8° C., or at least 1.9° C., or atleast 2.0° C., or at least 2.1 C, or at least 2.2° C., or at least 2.3°C., or at least 2.4° C., or at least 2.5 C, or at least 2.6° C., or atleast 2.7° C., or at least 2.8° C., or at least 2.9° C., or at least3.0° C., or at least 4.0° C., or at least 5.0° C. or more.

The differences in glass transition temperature between the firstplasticized resin and the second plasticized resin can be achieved byselecting the two resins to have different residual hydroxyl contents.In various embodiments, the second PVB resin in the soft core layer hasa residual hydroxyl content that differs by at least about 1.0 wt. %from the residual hydroxyl content of the first PVB resin, or at leastabout 1.5 wt. %, or at least about 2.0 wt. %, or at least about 2.5 wt.%, or at least about 3.0 wt. %, or at least about 3.5 wt. %, or at leastabout 4.0 wt. %, or at least about 4.5 wt. %, or at least about 5.0 wt.%, or at least about 5.5 wt. %, or at least about 6.0 wt. %, or at leastabout 6.5 wt. %, or at least about 7.0 wt. %, or at least about 7.5 wt.%, or at least about 8.0 wt. %, or at least about 8.5 wt. %, or at leastabout 9.0 wt. %, or at least about 9.5 wt. %, or at least about 10.0 wt.%, or at least about 10.5 wt. %, or at least about 11.0 wt. %, or atleast about 11.5 wt. %, or at least about 12 wt. % or more. Inparticularly useful embodiments, the residual hydroxyl content in thesecond resin differs from the first resin by about 1.0 wt. % to about7.0 wt. %. This difference between the first resin and the second resinis calculated by subtracting the residual hydroxyl content of the firstresin with the lower residual hydroxyl content from the residualhydroxyl content of the second resin with the greater residual hydroxylcontent (or taking the absolute value of the residual hydroxyl contentdifferences). For example, if a first resin has a residual hydroxylcontent of 12 wt. %, and a second polymer sheet has a residual hydroxylcontent of 15 wt. %, then the residual hydroxyl content of the tworesins differs by 3 wt. %, or the residual hydroxyl content in thesecond resin is 3 wt. % higher than the residual hydroxyl content in thesecond resin. The difference in the residual hydroxyl content betweenthe first resin and the second is controlled to impart enhanced soundinsulation performance to the interlayer, as discussed in fully detailsin the Examples.

The differences in glass transition temperature between the firstplasticized resin and the second plasticized resin can also be achievedby selecting the two resins such that they have the same residualhydroxyl content but different levels of residual vinyl acetate groupsor vinyl acetal group content. In various embodiments, the second PVBresin in the soft core layer has a residual hydroxyl content that is thesame as the residual hydroxyl content of the first resin but has a theresidual vinyl acetate content that differs from the residual vinylacetate content of the first PVB resin by at least about 1.5 mol %, orat least about 2.0 mol %, or at least about 3.0 mol %, or at least about4.0 mol %, or at least about 5.0 mol %, or at least about 6.0 mol %, orat least about 7.0 mol %, or at least about 8.0 mol %, or at least about9.0 mol %, or at least about 10.0 mol %, or at least about 11.0 mol %,or at least about 12.0 mol %, or at least about 13.0 mol %, or at leastabout 14.0 mol %, or at least about 15.0 mol % or more. In otherembodiments, the second PVB resin in the soft core layer has a residualhydroxyl content and a vinyl acetate content that are both differentfrom the first PVB resin.

In embodiments, the second PVB resin has vinyl isobutyral groups and thefirst resin has vinyl butyral groups; or the second resin contains2-ethylhexanal groups and the first resin contains vinyl butyral orvinyl isobutyral groups; or either the first or second resin or bothcontain a mixture of any two of vinyl butyral, vinyl isobutyral, or2-ethylhexanal groups.

In various embodiments of the present invention, the residual hydroxylcontent of the first resin in the core layer and the residual hydroxylcontent in the adjacent skin layer can differ by at least about 2.5 wt.%, or at least about 3.0 wt. %, or at least about 3.5 wt. %, or at leastabout 4.0 wt. %, or at least about 4.5 wt. %, or at least about 5.0 wt.%, or at least about 5.5 wt. %, or at least about 6.0 wt. %, or at leastabout 6.5 wt. %, or at least about 7.0 wt. %, or at least about 7.5 wt.%, or at least about 8.0 wt. %, or at least about 8.5 wt. %, or at leastabout 9.0 wt. %, or at least about 9.5 wt. %, or at least about 10.0 wt.%, or at least about 10.5 wt. %, or at least about 11.0 wt. %, or atleast about 11.5 wt. %, or at least about 12 wt. % or more. In someembodiments, the residual hydroxyl content in the second resin in thecore layer is greater than that of the first resin in the core layer andlower than the residual hydroxyl content of the resin in the skin layer.In further embodiments, the residual hydroxyl content in the secondresin in the core layer is lower than that of the first resin. Inexemplary embodiments, the higher residual hydroxyl contents of thefirst and the second resins are less than the residual hydroxyl contentof the resin in the skin layer and differs by at least 2.5 wt %, or atleast about 3.0 wt. %, or at least about 3.5 wt. %, or at least about4.0 wt. %, or at least about 4.5 wt. %, or at least about 5.0 wt. %, orat least about 5.5 wt. %, or at least about 6.0 wt. %, or at least about6.5 wt. %, or at least about 7.0 wt. %, or at least about 7.5 wt. %, orat least about 8.0 wt. %, or at least about 8.5 wt. %, or at least about9.0 wt. %, or at least about 9.5 wt. %, or at least about 10.0 wt. %, orat least about 10.5 wt. %, or at least about 11.0 wt. %, or at leastabout 11.5 wt. %, or at least about 12 wt. % or more. In otherembodiments, residual hydroxyl content of the resin in the skin layer isthe same as the residual hydroxyl content of one of the resins in thecore layer.

For a given type of plasticizer, the compatibility of that plasticizerin a poly(vinyl butyral) resin is largely determined by the hydroxylcontent. Typically, poly(vinyl butyral) with a greater residual hydroxylcontent will result in a reduced plasticizer compatibility or capacity.Likewise, poly(vinyl butyral) with a lower residual hydroxyl contentwill result in an increased plasticizer compatibility or capacity. Theseproperties can be used to select the hydroxyl content of each poly(vinylbutyral) polymer, fabricate core layer to have broad glass transition,and formulate each of the polymer sheet layers to allow for the properplasticizer loading and to stably maintain the differences inplasticizer content between the polymer layers and between the two ormore resins in the core layer.

FIG. 1 shows the damping loss factor at 10° C., 20° C., and 30° C. for adisclosed interlayer (DI-5) and a comparative interlayer (CI-2). Thedisclosed interlayer has a core layer containing a 50:50 blend of tworesins: a first resin having a residual hydroxyl content of 9.6 wt. %and a second resin having a residual hydroxyl content of about 11.5 wt.%, and an average residual hydroxyl of 10.5 wt. %; and 75 phrplasticizer. The comparative interlayer has a core layer containing asingle resin having a residual hydroxyl content of about 10.5 wt. % and75 phr plasticizer. Both interlayers have a core layer thickness of 10mils and a total interlayer thickness of 40 mils. The disclosedinterlayer having two resins shows improved damping loss factor at both10° C. and 20° C. while maintaining the damping loss factor at 30° C.(essentially unchanged compared to the comparative interlayer), thusproviding sound insulation over a broader range of temperatures (i.e.,from 10° C. to 20° C. to 30° C.), and particularly at lowertemperatures.

FIG. 2 shows the damping loss factor at 10° C., 20° C., and 30° C. for adisclosed interlayer (DI-14) and a comparative interlayer (CI-2). Thedisclosed interlayer has a core layer containing a 50:50 blend of tworesins: a first resin having a residual hydroxyl content of 9.6 wt. %and a second resin having a residual hydroxyl content of about 13 wt. %,and an average residual hydroxyl of 11.3 wt. %; and 70 phr plasticizer.The comparative interlayer has a core layer containing a single resinhaving a residual hydroxyl content of about 10.5 wt. % and 75 phrplasticizer. Both interlayers have a core layer thickness of 10 mils anda total interlayer thickness of 40 mils. The disclosed interlayer havingtwo resins shows improved damping loss factor at both 20° C. and 30° C.while maintaining the damping loss factor at 10° C. (essentiallyunchanged compared to the comparative interlayer), thus providing soundinsulation over a broader range of temperatures, and particularly athigher temperatures.

FIG. 3 shows the damping loss factor at 10° C., 20° C., and 30° C. for adisclosed interlayer (DI-24) and a comparative interlayer (CI-2). Thedisclosed interlayer has a core layer containing a 75:25 blend of tworesins: a first resin having a residual hydroxyl content of 9.6 wt. %and a second resin having a residual hydroxyl content of about 16.3 wt.%, and an average residual hydroxyl of 11.3 wt. %; and 75 phrplasticizer. The comparative interlayer has a core layer containing asingle resin having a residual hydroxyl content of about 10.5 wt. % and75 phr plasticizer. Both interlayers have a core layer thickness of 10mils and a total interlayer thickness of 40 mils. The disclosedinterlayer having two resins shows improved damping loss factor at allthree temperatures, thus providing sound insulation over a broader rangeof temperatures.

FIGS. 1 to 3 illustrate that by formulating the core layer in a multiplelayer interlayer to contain more than one resin, the sound insulationcan be improved at lower temperatures, higher temperatures, or over abroader range of temperatures. To broaden the sound insulationperformance over the temperature range of interest, the difference inthe residual hydroxyl content is controlled to be more than about 3 wt.%; to broaden the performance on one side of the temperature range thedifference in the residual hydroxyl content is selected to be less thanabout 3 wt. %. This difference in the residual hydroxyl content is alsoselected to affect the application temperature of glass panelscomprising the interlayer of present disclosure.

As is known in the art, residual hydroxyl content can be controlled bycontrolling reaction times, reactant concentrations, and other variablesin the manufacturing process. Examples of various embodiments of theresidual hydroxyl content of the two (or more) layers are as follows:the resin in the skin layer is less than 25 wt. %, the first resin inthe core layer is less than 22.5 wt. % and the second resin in the corelayer is less than 24 wt. %; or the skin layer less than 23 wt. % andthe two resins in the core layer are less than 20.5 wt. % and 22 wt. %,respectively; or the skin layer is less than 22 wt. % and the two resinsin the core layer are less than 16 wt. % and 18 wt. %, respectively; orthe skin layer is less than 22 wt. % and the two resins in the corelayer are less than 12 wt. % and 15 wt. %, respectively; or the skinlayer is less than 18 wt. % and the two resins in the core layer areless than 12 wt. % and 15 wt. %, respectively; or the skin layer is lessthan 15 wt. % and the two resins in the core layer are less than 10 wt.% and 12 wt. %, respectively. These are just examples of variousembodiments, and one skilled in the art would understand that in any ofthese embodiments, any of the values given in the previous paragraphsfor the difference in hydroxyl content between the resins in two (ormore) layers can be used.

In various embodiments, the first PVB resin in the core layer comprisesabout 6 to about 22 weight percent (wt. %) hydroxyl groups calculated as% PVOH, about 8 to about 14 wt. %, about 10 to about 14 wt. %, and forcertain embodiment, about 8 to about 12 wt. % hydroxyl groups calculatedas % PVOH. In various embodiment, the resin can also comprise less than30 wt. % residual ester groups, less than 25 wt. % residual estergroups, less than 20 wt. %, less than 15 wt. %, less than 13 wt. %, lessthan 10 wt. %, less than 7 wt. %, less than 5 wt. %, or less than 1 wt.% residual ester groups calculated as polyvinyl ester, e.g., acetate,with the balance being an acetal, such as butyraldehyde acetal, butoptionally being other acetal groups, such as an isobutyraldehyde acetalgroup, or a 2-ethyl hexanal acetal group, or a mix of any two ofbutyraldehyde acetal, isobutyraldehyde, and 2-ethyl hexanal acetalgroups.

In various embodiments, the second resin comprises about 6 to about 24wt. %, about 7 to about 18 wt. %, about 8 to about 16 wt. %, and forcertain embodiment, about 10 to about 14 wt. % hydroxyl groupscalculated as % PVOH. In various embodiments, the resin can alsocomprise less than about 30 wt. % residual ester groups, less than 25wt. % residual ester groups, less than 20 wt. %, less than 15 wt. %,less than 13 wt. %, less than 10 wt. %, less than 7 wt. %, less than 5wt. %, or less than 1 wt. % residual ester groups calculated aspolyvinyl ester, e.g., acetate, with the balance being an acetal, suchas butyraldehyde acetal, but optionally being other acetal groups, suchas an isobutyraldehyde acetal group, or a 2-ethyl hexanal acetal group,or a mix of any two of butyraldehyde acetal, isobutyraldehyde, and2-ethyl hexanal acetal groups.

In various embodiments, the resin in the skin layer can comprise about15 to about 35 wt. %, about 15 to about 30 wt. %, or about 17 to about22 wt. %; and, for certain embodiments, about 17.5 to about 22.5 wt. %residual hydroxyl groups calculated as % PVOH. In various embodiments,the first resin and the second resin for the core layer, or the resinfor the stiff layer(s), or any two of these resins, or all of the resinscan also comprise less than 30 wt. % residual ester groups, less than 25wt. % residual ester groups, less than 20 wt. %, less than 15 wt. %,less than 13 wt. %, less than 10 wt. %, less than 7 wt. %, less than 5wt. %, or less than 1 wt. % residual ester groups calculated aspolyvinyl ester, e.g., acetate, with the balance being an acetal, suchas butyraldehyde acetal, but optionally being other acetal groups, suchas an isobutyraldehyde, a 2-ethyl hexanal acetal group, or a mix of anytwo of butyraldehyde acetal, isobutyraldehyde acetal group, and 2-ethylhexanal acetal groups, as previously discussed.

The amount of the second resin relative to the first resin can vary inany range, as desired, such as from 1 to 99 wt. %, 2 to 98 wt. %, 3 to97 wt. %, 4 to 96 wt. %, 5 to 95 wt. %, 10 to 90 wt. %, 15 to 85 wt. %,20 to 80 wt. %, 25 to 75 wt. %, or about 50 wt. % of each in the corelayer. The amount of the second resin may be any amount, from about 1wt. % up to about 99 wt. %, depending on the desired properties. Incertain embodiments, the amount of the second resin varies from about 25to about 75 wt. %.

In various embodiments, the core layer comprises more than two resins.The differences in composition between any two of the resins can be anyof the differences given above for the differences between the firstresin and the second resin. For more than two resins, each resin can beincluded in amounts of at least 1 wt. % or more, or at least 2 wt. %, orat least 3 wt. %, or at least 4 wt. %, or at least 5 wt. % up to 98 wt%, depending on the desired properties of the polymer interlayer and thespecific properties of the resins.

The amount of plasticizer in the interlayer can be adjusted to affectthe glass transition temperature (T_(g)). In general, higher amounts ofplasticizer loading will result in lower T_(g). Because the plasticizerwill partition such that there is more plasticizer in the polymer resinhaving the lower residual hydroxyl content and less plasticizer in thePVB resin having the higher residual hydroxyl content, the amount ofplasticizer can be adjusted to shift the glass transition of the corelayer and the temperature at which the interlayer exhibits optimum soundinsulation property.

In various embodiments of present disclosure, the interlayer comprisesgreater than 5 phr, about 5 to about 120 phr, about 10 to about 90 phr,about 20 to about 70 phr, about 30 to about 60 phr, or less than 120phr, or less than 90 phr, or less than 60 phr, or less than 40 phr, orless than 30 phr total plasticizer. The total plasticizer content in theinterlayer is adjusted to affect the glass transitions of the core layerto optimize sound insulation property of the interlayer at a givenapplication temperature range. The plasticizer content in the skinlayer(s) or core layer(s) can be different from the total plasticizercontent. In addition, the skin layer(s) and core layer(s) can havedifferent plasticizer types and plasticizer contents, in the rangesdiscussed above, and as each respective layer's plasticizer content atthe equilibrium state is determined by the layer's respective residualhydroxyl contents, as disclosed in U.S. Pat. No. 7,510,771 (the entiredisclosure of which is incorporated herein by reference). For example,at equilibrium the interlayer could comprise two skin layers, each with30 phr plasticizer, and a core layer with 65 phr plasticizer, for atotal plasticizer amount for the interlayer of about 45.4 phr when thecombined skin layer thickness equals that of the core layer. For thickeror thinner skin layers, the total plasticizer amount for the interlayerwould change accordingly. In various embodiments of the presentinvention, the plasticizer content of the core layer and skin layerdiffers by at least 8 phr, or at least 9 phr, or at least 10 phr, or atleast 12 phr, or at least 13 phr, or at least 14 phr, or at least 15phr, or at least 16 phr, or at least 17 phr, or at least 18 phr, or atleast 19 phr, or at least 20 phr, or at least 25 phr or more. As usedherein, the amount of plasticizer, or any other component in theinterlayer, can be measured as parts per hundred parts resin (phr), on aweight per weight basis. For example, if 30 grams of plasticizer isadded to 100 grams of polymer resin, then the plasticizer content of theresulting plasticized polymer would be 30 phr. As used herein, when theplasticizer content of the interlayer is given, the plasticizer contentis determined with reference to the phr of the plasticizer in the mix ormelt that was used to produce the interlayer.

In various embodiments, the plasticizer is selected from conventionalplasticizers, a mixture of two or more conventional plasticizers. Insome embodiments, the conventional plasticizer, which has refractiveindex of less than about 1.450, may include, for example, triethyleneglycol di-(2-ethylhexanoate) (“3GEH”), triethylene glycoldi-(2-ethylbutyrate), triethylene glycol diheptanoate, tetraethyleneglycol diheptanoate, tetraethylene glycol di-(2-ethylhexanoate), dihexyladipate, dioctyl adipate, hexyl cyclohexyladipate, diisononyl adipate,heptylnonyl adipate, dibutyl sebacate, dioctyl sebacate, di(butoxyethyl)adipate, bis(2-(2-butoxyethoxy)ethyl) adipate, and mixtures thereof. Insome embodiments, the conventional plasticizer is 3GEH (Refractiveindex=1.442 at 25° C.).

In some embodiments, other plasticizers known to one skilled in the artmay be used, such as a plasticizer with a higher refractive index (i.e.,a high refractive index plasticizer). As used herein, a “high refractiveindex plasticizer” is a plasticizer having a refractive index of atleast about 1.460. As used herein, the refractive index (also known asindex of refraction) of a plasticizer or a resin used in the entirety ofthis disclosure is either measured in accordance with ASTM D542 at awavelength of 589 nm and 25° C. or reported in literature in accordancewith ASTM D542. In various embodiments, the refractive index of theplasticizer is at least about 1.460, or greater than about 1.470, orgreater than about 1.480, or greater than about 1.490, or greater thanabout 1.500, or greater than 1.510, or greater than 1.520, for both coreand skin layers. In some embodiments, the high refractive indexplasticizer(s) is used in conjunction with a conventional plasticizer,and in some embodiments, if included, the conventional plasticizer is3GEH, and the refractive index of the plasticizer mixture is at least1.460.

Examples of plasticizers having a high refractive index that may be usedinclude, but are not limited to, polyadipates (RI of about 1.460 toabout 1.485); epoxides (RI of about 1.460 to about 1.480); phthalatesand terephthalates (RI of about 1.480 to about 1.540); benzoates (RI ofabout 1.480 to about 1.550); and other specialty plasticizers (RI ofabout 1.490 to about 1.520). Examples of the high refractive indexplasticizer include, but are not limited to, esters of a polybasic acidor a polyhydric alcohol, polyadipates, epoxides, phthalates,terephthalates, benzoates, toluates, mellitates and other specialtyplasticizers, among others. Examples of suitable plasticizers include,but are not limited to, dipropylene glycol dibenzoate, tripropyleneglycol dibenzoate, polypropylene glycol dibenzoate, isodecyl benzoate,2-ethylhexyl benzoate, diethylene glycol benzoate, propylene glycoldibenzoate, 2,2,4-trimethyl-1,3-pentanediol dibenzoate,2,2,4-trimethyl-1,3-pentanediol benzoate isobutyrate, 1,3-butanedioldibenzoate, diethylene glycol di-o-toluate, triethylene glycoldi-o-toluate, dipropylene glycol di-o-toluate, 1,2-octyl dibenzoate,tri-2-ethylhexyl trimellitate, di-2-ethylhexyl terephthalate, bis-phenolA bis(2-ethylhexaonate), ethoxylated nonylphenol, and mixtures thereof.

In embodiments having more than two layers, the polymer interlayer maycomprise a second, or an additional skin layer (second skin layer) thatis disposed in contact with the soft layer having the higher plasticizercontent. Addition of this polymer layer results in a three layerconstruct that has the following structure: first skin layer//corelayer//second skin layer. This second skin layer can have the samecomposition as the first skin layer, or it can be different.

In various embodiments, the second skin layer has the same compositionas the first skin layer. In other embodiments, the second skin layer hasa different composition than the first skin layer, and the differencesin composition between the second skin layer and the core layer can beany of the differences given above for the differences between the firstskin layer and the core layer. For example, one exemplary embodimentwould be: first skin layer with a residual hydroxyl content of 20 wt.%//core layer with first resin having a residual hydroxyl content of15.5 wt. % and second resin having a residual hydroxyl content of 17 wt.%//second skin layer with a residual hydroxyl content of 18 wt. %. Itwill be noted that, in this example, the skin layer differs from thefirst resin in the core layer at least in that it has a residualhydroxyl content that is 2.5 wt. % greater than the hydroxyl content ofthe first resin. Of course, any of the other differences noted hereinthroughout can singly or in combination distinguish the second skinlayer from the core layer.

In addition to the two or three layer embodiments described herein,further embodiments include interlayers having more than three layers inwhich further layers having different residual hydroxyl layers can beused, for example, iterations of polymer layers having alternatingplasticizer contents with alternating hydroxyl contents and optionallyresidual acetate content of 1 to 30 wt. %. Interlayers formed in such amanner can have, for example, 4, 5, 6, or up to 10 or more individuallayers.

Generally, the thickness, or gauge, of the polymer interlayer will be ina range from about 0.25 mm to about 2.54 mm (about 10 mils to 100 mils),about 0.38 mm to about 1.52 mm (about 15 mils to 60 mils), about 0.51 to1.27 mm (about 20 mils to about 50 mils), and about 0.38 to about 0.89mm (about 15 mils to about 35 mils). In various embodiments, each of thelayers, such as the skin and core layers, of the multilayer interlayermay have a thickness of about 1 mil to 99 mils (about 0.025 to 2.51 mm),about 1 mil to 59 mils (about 0.025 to 1.50 mm), 1 mil to about 29 mils(about 0.025 to 0.74 mm), or about 2 mils to about 28 mils (about 0.05to 0.71 mm).

The final interlayer, whether formed from extrusion or co-extrusion,generally has a random rough surface topography as it is formed throughmelt fractures of polymer melt as it exits the extrusion die and mayadditionally be embossed over the random rough surface on one or bothsides (e.g., the skin layers) by any method of embossment known to oneof ordinary skill in the art.

In various embodiments, the polymer can be any polymer suitable for usein a multiple layer panel. Typical polymers include, but are not limitedto, polyvinyl acetals (PVA) (such as poly(vinyl butyral) (PVB) orpoly(vinyl isobutyral), an isomer of poly(vinyl butyral) and alsoreferred as PVB, aliphatic polyurethane (PU), poly(ethylene-co-vinylacetate) (EVA), polyvinylchloride (PVC),poly(vinylchloride-co-methacrylate), polyethylenes, polyolefins,ethylene acrylate ester copolymers, poly(ethylene-co-butyl acrylate),silicone elastomers, epoxy resins, and acid copolymers such asethylene/carboxylic acid copolymers and its ionomers, derived from anyof the foregoing possible thermoplastic resins, combinations of theforegoing, and the like. PVB and its isomer polyvinyl isobutyral,polyvinyl chloride, ionomers, and polyurethane are suitable polymersgenerally for interlayers; PVB and its isomer are particularly suitable.Polyurethanes can have different hardnesses. An exemplary polyurethanepolymer has a Shore A hardness less than 85 per ASTM D-2240. Examples ofpolyurethane polymers are AG8451 and AG5050, aliphatic isocyanatepolyether based polyurethanes having glass transition temperatures lessthan 20° C. (commercially available from Thermedics Inc. of Woburn,Mass.). EVA polymers (or copolymers) can contain various amounts ofvinyl acetate groups. The desirable vinyl acetate content is generallyfrom about 10 to about 90 mol %. EVA with lower vinyl acetate contentcan be used for sound insulation at low temperatures. Theethylene/carboxylic acid copolymers are generallypoly(ethylene-co-methacrylic acid) and poly(ethylene-co-acrylic acid)with the carboxylic acid content from 1 to 25 mole %. Ionomers ofethylene/carboxylic acid copolymers can be obtained by partially orfully neutralizing the copolymers with a base, such as the hydroxide ofalkali (sodium for example) and alkaline metals (magnesium for example),ammonia, or other hydroxides of transition metals such as zinc. Examplesof ionomers of that are suitable include Surlyn® ionomers resins(commercially available from DuPont of Wilmington, Del.).

Examples of exemplary multilayer interlayer constructs include, but arenot limited to, PVB//PVisoB//PVB, where PVisoB layer comprises two ormore resins having different residual hydroxyl contents or differentpolymer compositions; PVC//PVB//PVC, PU//PVB//PU, Ionomer//PVB//Ionomer,Ionomer//PU//Ionomer, Ionomer//EVA//Ionomer, where the core layer PVB(including PVisoB), PU or EVA comprises two or more resins havingdifferent glass transitions. Alternatively, the skin and core layers mayall be PVB using the same or different starting resins. Othercombinations of resins and polymers will be apparent to those skilled inthe art.

The sound insulation effect over a broad temperature range that ischaracteristic of the multilayer interlayers disclosed herein isachieved in a single polymer interlayer through the use of co-extrusionprocesses. For each interlayer embodiment of the present invention inwhich two or more separate polymer layers are disposed in contact withone another and subsequently laminated into a single interlayer, therealso exists an embodiment where a coextruded polymer sheet has two ormore distinct layers corresponding to the individual layers in alaminated interlayer of the present invention. Further, for each of themultiple layer glass panels, methods of producing interlayers, andmethods of producing multiple layer glass panels of the presentinvention in which separate polymer layers are laminated together, thereis also an analogous embodiment employing a coextruded polymer layers inplace of the multiple layer interlayer.

The present invention also includes methods of manufacturing aninterlayer, comprising the steps of forming a first polymer layer and asecond polymer layer comprising two or more resins of differentcompositions, wherein the two polymer layers have differentcompositions, as described herein, and laminating the two polymer sheetstogether to form the interlayer.

The present invention also includes methods of manufacturing aninterlayer, comprising the steps of forming a first polymer layer, asecond polymer layer comprising two or more resins of differentcompositions, and a third polymer layer, wherein the three polymerlayers have compositions according to the three layer embodiments asdescribed herein, and laminating the three polymer layers together toform the interlayer.

The present invention also includes the interlayers comprising variousadhesion control agents (“ACAs”). Such ACAs, include, but are notlimited to, the ACAs disclosed in U.S. Pat. No. 5,728,472 (the entiredisclosure of which is incorporated herein by reference), residualsodium acetate, potassium acetate, magnesium bis(2-ethyl butyrate),and/or magnesium bis(2-ethylhexanoate).

The present invention also includes additives to impart certainadditional properties to the interlayer. Such additives include, but arenot limited to, dyes, pigments, stabilizers (e.g., ultravioletstabilizers), antioxidants, anti-blocking agents, flame retardants, IRabsorbers or blockers (e.g., indium tin oxide, antimony tin oxide,lanthanum hexaboride (LaB₆) and cesium tungsten oxide), processingaides, flow enhancing additives, lubricants, impact modifiers,nucleating agents, thermal stabilizers, UV absorbers, dispersants,surfactants, chelating agents, coupling agents, adhesives, primers,reinforcement additives, and fillers, among other additives known tothose of ordinary skill in the art.

The present invention also includes a single substrate, such as glass,acrylic, or polycarbonate with a polymer interlayer sheet disposedthereon, and most commonly, with a polymer film further disposed overthe polymer interlayer. The combination of polymer interlayer sheet andpolymer film is commonly referred to in the art as a bilayer. A typicalmultiple layer panel with a bilayer construct is: (glass) II (polymerinterlayer sheet) II (polymer film), where the polymer interlayer sheetcan comprise multiple interlayers, as noted above.

The present invention also includes methods of manufacturing a multiplelayer glazing, comprising laminating any of the interlayers of thepresent invention between two rigid, transparent panels, as are known inthe art, such as glass or acrylic layers.

The present invention also includes multiple layer glass panels, such aswindshields and architectural windows, comprising a multilayerinterlayer of the present invention. Also included are multiple layerglazing panels having plastics, such as acrylics, or other suitablematerials in place of the glass panels.

These examples of multiple layer panels are in no way meant to belimiting, as one of ordinary skill in the art would readily recognizethat numerous constructs other than those described above could be madewith the interlayers of the present disclosure.

Clarity is a parameter used to describe the polymer interlayersdisclosed herein. Clarity is determined by measuring the haze value orpercent haze. The test for percent haze is performed with a hazemeter,such as Model D25 available from Hunter Associates (Reston, Va.), and inaccordance with ASTM D1003-61 (Re-approved 1977)-Procedure A usingIlluminant C, at an observer angle of 2 degrees. The polymer interlayersare laminated with a pair of clear glass sheets each of 2.3 mm thick(commercially available from Pittsburgh Glass Works of Pennsylvania) andthe haze values are measured. The interlayers of the present disclosurehave a percent haze of less than about 5%, less than about 4%, less thanabout 3%, less than about 2%, less than about 1%, or less than about0.5%.

Transparency, or percent visual transmittance (% T_(vis)) is also usedto describe the polymer interlayers disclosed herein. The transparencyis measured with a hazemeter, such as Model D25 available from HunterAssociates (Reston, Va.), and in Illuminant D65, at an observer angle of10 degrees. The polymer interlayers are laminated with a pair of clearglass sheets each of 2.3 mm thick (commercially available fromPittsburgh Glass Works of Pennsylvania) and the % T_(vis) are measured.The polymer interlayers of the present disclosure have a % T_(vis) ofgreater than 85 for the interlayers containing only additives of ACAs,UV stabilizers, and antioxidant, or greater than 80% for the interlayerscontaining additional additives such as pigments, IR absorbers orblockers as mentioned above. Polymer interlayers containing high levelsof pigments and/or dyes may have lower % T_(vis) values as desired, suchas in mass pigmented or colored polymer interlayers.

The refractive index (RI) was measured in accordance with ASTM D542. Thereported RI values are obtained at a wavelength of 589 nm and at 25° C.

The sound insulation property, such as Sound Transmission Loss, of aglass panel comprising interlayer of the present invention is evaluatedby the damping loss factor value obtained from vibration measurements.Sound transmission loss of a glass panel correlates with damping lossfactor of the panel (see, for example, Lu, J: “Designing PVB Interlayerfor Laminated Glass with Enhanced Sound Reduction”, 2002, InterNoise2002, paper 582). The damping loss factor (η) was measured by MechanicalImpedance Measurement as described in ISO 16940. A laminated glass barsample of 25 mm wide, 300 mm long, and having a pair of 2.3 mm clearglass is prepared and excited at the center point of the bar by avibration shaker (Brüel and Kjær). An impedance head (Brüel and Kjær) isused to measure the force to excite the bar to vibrate and the velocityof the vibration and the resultant transfer function is recorded on aNational Instrument data acquisition and analysis system. The dampingloss factor at the first vibration mode is calculated using thehalf-power method. Higher damping loss factor means better soundinsulation performance.

The invention also includes Embodiments 1 to 12, as set forth below.

Embodiment 1 is a polymer interlayer having improved sound insulation,the polymer interlayer comprising: at least one soft layer wherein thesoft layer comprises: a first poly(vinyl butyral) resin having a firstresidual hydroxyl content and a first glass transition temperature(T_(g)); a second poly(vinyl butyral) resin having a second residualhydroxyl content and a second glass transition temperature (T_(g)),wherein the difference between the first residual hydroxyl content andthe second residual hydroxyl content is at least 1.0 weight percent;wherein the difference between the first glass transition temperature(T_(g)) the second glass transition temperature (T_(g)) is at least 1.5°C.; and a plasticizer; at least one stiffer layer comprising a thirdpoly(vinyl butyral resin) having a third residual hydroxyl content; anda plasticizer, wherein the polymer interlayer has a damping loss factor(η) (as measured by Mechanical Impedance Measurement according to ISO16940) of at least about 0.16 measured at two or more differenttemperatures selected from 10° C., 20° C. and 30° C.

Embodiment 2 is polymer interlayer having improved sound insulation, thepolymer interlayer comprising: at least one soft layer wherein the softlayer comprises: a first poly(vinyl butyral) resin having a firstresidual hydroxyl content and a first glass transition temperature(T_(g)); a second poly(vinyl butyral) resin having a second residualhydroxyl content and a second glass transition temperature (T_(g)),wherein the difference between the first residual hydroxyl content andthe second residual hydroxyl content is at least 1.0 weight percent,wherein the difference between the first glass transition temperature(T_(g)) and the second glass transition temperature (T_(g)) is at least1.5° C.; and a plasticizer; at least one stiffer layer comprising athird poly(vinyl butyral resin) having a third residual hydroxylcontent; and a plasticizer, wherein each plasticized resin in the softlayer of the polymer interlayer has a glass transition temperature(T_(g)) less than 20.0° C.

Embodiment 3 is a polymer interlayer having improved sound insulation,the polymer interlayer comprising: at least one soft layer wherein thesoft layer comprises: a first poly(vinyl butyral) resin having a firstresidual hydroxyl content and a first glass transition temperature(T_(g)); a second poly(vinyl butyral) resin having a second residualhydroxyl content and a second glass transition temperature (T_(g)),wherein the difference between the first residual hydroxyl content andthe second residual hydroxyl content is at least 1.0 weight percent;wherein the difference between the first glass transition temperature(T_(g)) the second glass transition temperature (T_(g)) is at least 1.5°C.; and a plasticizer; at least one stiffer layer comprising a thirdpoly(vinyl butyral resin) having a third residual hydroxyl content; anda plasticizer, wherein the polymer interlayer has a damping loss factor(η) (as measured by Mechanical Impedance Measurement according to ISO16940) of at least about 0.16 measured at two or more differenttemperatures selected from 10° C., 20° C. and 30° C., and wherein thesecond poly(vinyl butyral) resin is present in an amount of from about 5weight percent to about 50 weight percent.

Embodiment 4 is a polymer interlayer including any of the features ofembodiments 1 to 2, wherein the second poly(vinyl butyral) resin ispresent in an amount of from about 5 weight percent to about 50 weightpercent.

Embodiment 5 is a polymer interlayer including any of the features ofembodiments 1 to 4, wherein the second poly(vinyl butyral) resin ispresent in an amount of from about 25 weight percent to about 50 weightpercent.

Embodiment 6 is a polymer interlayer including any of the features ofembodiments 1 or 3, wherein each plasticized resin in the soft layer ofthe polymer interlayer has a glass transition temperature (T_(g)) lessthan 20.0° C.

Embodiment 7 is a polymer interlayer including any of the features ofembodiments 1 to 6, wherein the residual hydroxyl content of the thirdpoly(vinyl butyral resin) is the same as the residual hydroxyl contentof the first poly(vinyl butyral resin) or the second poly(vinyl butyralresin).

Embodiment 8 is a polymer interlayer including any of the features ofembodiments 1 to 7, wherein the difference between the first residualhydroxyl content and the second residual hydroxyl content is at least2.0 weight percent.

Embodiment 9 is a polymer interlayer including any of the features ofembodiments 1 to 8, wherein the difference between the first residualhydroxyl content and the second residual hydroxyl content is at least3.0 weight percent

Embodiment 10 is a polymer interlayer including any of the features ofembodiments 1 to 9, wherein the difference between the glass transitiontemperatures (T_(g)) of the first poly(vinyl butyral) resin and thesecond poly(vinyl butyral) resin is at least 3.0° C.

Embodiment 11 is a multiple layer glass panel including the polymerinterlayer of any of embodiments 1 to 10.

Embodiment 12 is a multiple layer glass panel comprising: a first glasspanel; a polymer interlayer including any of the features of embodiments1 to 10, a second glass panel, wherein the polymer interlayer isdisposed between the first and second glass panels.

EXAMPLES

Exemplary core layers of the present disclosure (designated as“Disclosed Layers” and as shown as DL 1-16 in the Tables below) andcomparative core layers (designated as “Comparative Layers” and as shownas CL 1-3 in the Tables below) were produced by mixing andmelt-extruding 100 parts poly(vinyl butyral) resin(s) and variousamounts of 3GEH plasticizer, and other common additives (as describedabove), as shown below. For the Disclosed Layers, the types and amounts(ratio) of the two resins is also shown. The core layers were then usedto construct various multilayered interlayers as shown in the Tables andas described more fully below. The skin layers each had a thickness of15 mils in the multilayer interlayers (CI-1 to CI-4 and DI-1 to DI-26)and contain 100 parts poly(vinyl butyral) resin having a residualhydroxyl content of about 19 wt. % and a residual acetate content of 2%,and 38 parts 3GEH plasticizer, and other common additives (as describedabove). The multilayer interlayers all have the construction: Skinlayer//Core layer//Skin layer.

The improved sound damping properties of a multilayer interlayer can bemost readily appreciated by a comparison of multilayer (tri-layer)interlayers having a blend of two resins of different residual hydroxylcontents and different glass transition temperatures and at least oneplasticizer in the core layer (designated as “Disclosed Interlayers”) toa multilayer interlayer having a core layer formed from only a singleresin (of a fixed residual hydroxyl content) and at least oneplasticizer in the core layer (designated as “Comparative Interlayers”).The Comparative Interlayers are shown as CI-1 to CI-4, and the DisclosedInterlayers are shown as DI-1 to DI-26 in the Tables. These Examplesdemonstrate that the sound damping properties can be improved andachieved over a range of temperatures when at least two PVB resinshaving differing residual hydroxyl contents and glass transitiontemperatures are used in the core layer, such as when a second PVB resinhaving a higher residual hydroxyl content and different glass transitiontemperature is added to (or combined with) a first PVB resin having alower residual hydroxyl level the core layer.

The resins used in the Tables below are PVB resins having residualhydroxyl contents and vinyl acetate residues as follows:

Resin-A: about 10.5 wt. % residual hydroxyl content and a vinyl acetateresidue of 2%.

Resin-B: about 9.6 wt. % residual hydroxyl content and a vinyl acetateresidue of 2%.

Resin-C: about 13 wt. % residual hydroxyl content and a vinyl acetateresidue of 2%.

Resin-D: about 16.3 wt. % residual hydroxyl content and a vinyl acetateresidue of 2%.

Resin-E: about 11.5 wt. % residual hydroxyl content and a vinyl acetateresidue of 2%.

In the Tables below, core layers constructed from different combinationsof two resins having different residual hydroxyl contents and glasstransition temperatures are compared to core layers comprising only oneresin at a fixed residual hydroxyl content. Glass transitiontemperatures of the plasticized first and second resins as well as theobserved glass transition temperatures and damping loss factors areshown in the Tables below.

TABLE 1 Core layer Glass transition Observed First Second temperaturesof Core resin resin Average individual layer glass Damping residualresidual residual Plas- plasticized transition loss factor Inter- CorePVB Ratio hydroxyl hydroxyl hydroxyl ticizer thick- resins (° C.)temperatures (η) at tem- layer layer resin(s) of content content contentcontent ness First Second (° C.) perature (° C.) No no. Used B/E (wt. %)(wt. %) (wt. %) (phr) (mil) T_(g1) T_(g2) T_(g1) 10 20 30 CI-1 CL-1 A —10.5 — 10.5 75  5 −2.5 — −2.5 0.27 0.44 0.27 DI-1 DL-1 B, E 50/50  9.611.5 10.5 75  5 −4.5 1.9 0.2 0.34 0.50 0.24 DI-2 DL-2 B, E 50/50  9.611.5 10.5 70  5 −2.2 3.7 1.4 0.39 0.54 0.27 DI-3 DL-3 B, E 50/50  9.611.5 10.5 65  5 0.4 5.8 3.4 0.21 0.52 0.34 DI-4 DL-4 B, E 50/50  9.611.5 10.5 60  5 3 8.1 6.2 0.20 0.51 0.36 CI-2 CL-1 A — 10.5 — 10.5 75 10−2.5 — −2.5 0.28 0.45 0.26 DI-5 DL-1 B, E 50/50  9.6 11.5 10.5 75 10−4.5 1.9 0.2 0.42 0.50 0.25 DI-6 DL-2 B, E 50/50  9.6 11.5 10.5 70 10−2.2 3.7 1.4 0.37 0.54 0.25 DI-7 DL-3 B, E 50/50  9.6 11.5 10.5 65 100.4 5.8 3.4 0.31 0.56 0.28 DI-8 DL-4 B, E 50/50  9.6 11.5 10.5 60 10 38.1 6.2 0.27 0.62 0.34

Table 1 compares interlayers having comparative core layers formed fromone resin having a residual hydroxyl content of about 10.5 wt. % withdisclosed core layers comprising two resins at a resin ratio of 50:50,with an average residual hydroxyl content of about 10.5 wt. %, and adelta residual hydroxyl content of about 1.9 wt. %. Core layers wereformed in two thicknesses, 5 mils and 10 mils, and at varyingplasticizer levels of from 60 phr to 75 phr. Glass transitiontemperatures for the individual plasticized resins are shown, as well asthe observed glass transition temperature of the core layer. Since theindividual glass transition temperatures do not differ by a largeamount, only one glass transition temperature was seen and measured onthe core layer, which is between the two individual glass transitiontemperatures.

Damping loss factor was measured on all the interlayers, as shown inTable 1. For the 5 mils core layers, at plasticizer levels of 70 and 75phr, damping loss factors are higher at 10° C. and 20° C. andessentially unchanged at 30° C. when compared to that of the controlsample. For the 10 mils core layers, the same but more pronounced trendswere observed. At plasticizer levels of 65, 70 and 75 phr, damping lossfactors are higher at 10° C. and 20° C. and essentially unchanged at 30°C. At 60 phr, the damping loss factor increased at 20° C. and 30° C. andremained unchanged at 10° C.

These examples illustrate the benefit of incorporating two resins ofdifferent residual hydroxyl contents (9.6 and 11.5 wt. %, respectively)in the core layer with the average residual hydroxyl content level equalto the residual hydroxyl level of the single resin of the controlsample, the sound insulation property of the multilayer interlayer isimproved and broadened in the temperature range of 10° C. to 30° C. Bymodulating the amount of plasticizer in the core, the sound insulationproperty can be improved at either higher or lower temperature end. Thisis clearly illustrated by comparing the control interlayer, CI-1, wherethe damping loss factor is maximized at 20° C. (and it decreases at both10° C. and 30° C.) with the disclosed interlayers, such as DI-1 andDI-2, where the damping loss factor is also maximized at 20° C. but alsoincreases at 10° C. and remains almost unchanged at 30° C. For thedisclosed interlayers, DI-3 and DI-4, the damping loss factor is alsomaximized at 20° C. but also increases at 30° C. Comparing CI-2 withDI-5, DI-6 and DI-7 shows a similar trend, where the damping loss factoris maximized at 20° C. (and it decreases at both 10° C. and 30° C.) forthe control sample while the damping loss factor is also maximized at20° C. but also increases at 10° C. and remains almost unchanged at 30°C. for the disclosed interlayers. For the disclosed interlayer, DI-8,the damping loss factor is also maximized at 20° C. but also increasesat 30° C. while remaining essentially unchanged at 10° C., providingbetter sound insulation over a broader range of temperatures.

TABLE 2 Core layer Glass transition Observed First Second temperaturesof Core resin resin Average individual layer glass Damping residualresidual residual Plas- plasticized transition loss factor Inter- CorePVB Ratio hydroxyl hydroxyl hydroxyl ticizer thick- resins (° C.)temperatures (η) at tem- layer layer resin(s) of content content contentcontent ness First Second (° C.) perature (° C.) No no. Used B/C (wt. %)(wt. %) (wt. %) (phr) (mil) T_(g1) T_(g2) T_(g1) 10 20 30 CI-1 CL-1 A —10.5 — 10.5 75  5 −2 — −2.5 0.27 0.44 0.27 DI-9 DL-5 B, C 50/50  9.6 1311.3 75  5 −4.5 4.9 −1.0 0.17 0.40 0.34 DI-10 DL-6 B, C 50/50  9.6 1311.3 70  5 −2.2 6.7 1.0 0.14 0.34 0.33 DI-11 DL-7 B, C 50/50  9.6 1311.3 65  5 0.4 8.7 3.8 0.10 0.33 0.40 DI-12 DL-8 B, C 50/50  9.6 13 11.360  5 3 10.3 6.3 0.12 0.36 0.40 CI-2 CL-1 A — 10.5 — 10.5 75 10 −2 —−2.5 0.28 0.45 0.26 DI-13 DL-5 B, C 50/50  9.6 13 11.3 75 10 −4.5 4.9−1.0 0.34 0.49 0.28 DI-14 DL-6 B, C 50/50  9.6 13 11.3 70 10 −2.2 6.71.0 0.25 0.55 0.40 DI-15 DL-7 B, C 50/50  9.6 13 11.3 65 10 0.4 8.7 3.80.21 0.55 0.41 DI-16 DL-8 B, C 50/50  9.6 13 11.3 60 10 3 10.3 6.3 0.150.47 0.42

Table 2 compares interlayers having comparative core layers with aresidual hydroxyl content of about 10.5 wt. % with disclosed core layerscomprising two resins with an average residual hydroxyl content of about11.3 wt. %, and a delta residual hydroxyl content of about 3.4 wt. %.Core layers were formed in two thicknesses, 5 mils and 10 mils, and atvarying plasticizer levels of from 60 phr to 75 phr. Glass transitiontemperatures for the individual plasticized resins are shown, as well asthe glass transition temperature of the core layer. Since the individualglass transition temperatures do not differ by a large amount, only oneglass transition temperature is measured on the core layer, which isbetween the two individual glass transition temperatures.

Damping loss factor was measured on all the interlayers, as shown inTable 2. For the 5 mils core layers, at plasticizer levels of 60, 65, 70and 75 phr, damping loss factor is lower than that of the control sampleat 10° C. and 20° C. and higher at 30° C. The lower damping loss factorsat 10° C. and 20° C. are due to higher average residual hydroxyl contentof 11.3 (vs. 10.5 for the control) and the core layer thickness of 5mils. When the core layer thickness is increased from 5 mils to 10 mils,there is a significant increase in damping loss factor at 10° C. and 20°C. At a plasticizer level of 75 phr, the damping loss factor of thedisclosed interlayers is better than that of the control or comparativeinterlayers at all three temperatures. When reducing the plasticizerlevel to 70 phr or 60 phr, there is a reduction in damping loss factorat 10° C., but the damping loss factor improves further at both 20° C.and 30° C. Therefore, even with higher averaging residual hydroxylcontent in the core layer, the sound insulation of the interlayers canbe improved over a broader temperature range by increasing the corelayer thickness.

This is clearly illustrated by comparing the control interlayer, CI-1,where the damping loss factor is maximized at 20° C. (and it decreasesat both 10° C. and 30° C.) with the disclosed interlayers, such as DI-9,DI-10, DI-11 and DI-12, where the damping loss factor is also maximizedat 20° C. but also increases at 30° C. The same trend is shown whencomparing the core layers at the thickness of 10 mils, where for CI-2,the damping loss factor is maximized at 20° C. (and it decreases at both10° C. and 30° C.), but for DI-13, DI-14, DI-15 and DI-16, the dampingloss factor is also maximized at 20° C. but also increases at 30° C.,providing better sound insulation over a broader range of temperatures.For DI-13, DI-14 and DI-15, the damping loss factor at 10° C. is stillat least 0.20.

TABLE 3 Core layer Glass transition Observed Core First Secondtemperatures of layer glass resin resin Average individual transitionDamping residual residual residual Plas- plasticized temperatures lossfactor Inter- Core PVB Ratio hydroxyl hydroxyl hydroxyl ticizer thick-resins (° C.) (° C.) (η) at tem- layer layer resin(s) of content contentcontent content ness First Second First Second perature (° C.) No no.Used B/D (wt. %) (wt. %) (wt. %) (phr) (mil) T_(g1) T_(g2) T_(g1) T_(g2)10 20 30 CI-3 CL-2 C 13 13 65 5 8.7 — 8.7 — 0.06 0.24 0.45 CI-4 CL-3 C13 13 60 5 10.3 — 10.3 — 0.05 0.21 0.43 DI-17 DL-9 B, D 50/50 9.6 16.313 65 5 0.4 12.3 −3.4 14 0.08 0.27 0.49 DI-18 DL-10 B, D 50/50 9.6 16.313 60 5 3 14.5 −1 15.9 0.06 0.18 0.41 DI-19 DL-9 B, D 50/50 9.6 16.3 1365 10 0.4 12.3 −3.4 14 0.20 0.47 0.39 DI-20 DL-10 B, D 50/50 9.6 16.3 1360 10 3 14.5 −1 15.9 0.15 0.42 0.41

Table 3 compares interlayers having comparative core layers with aresidual hydroxyl content of about 13 wt. % with disclosed core layerscomprising two resins with an average residual hydroxyl content of about13 wt. %, and a delta residual hydroxyl content of about 6.7 wt. %. Corelayers were formed in two thicknesses, 5 mils and 10 mils, and atvarying plasticizer levels of 60 phr and 65 phr. Glass transitiontemperatures for the individual plasticized resins are shown, as well asthe glass transition temperatures of the core layer. At the higher deltaresidual hydroxyl level, the two different glass transition temperaturesare measurable in the Disclosed Interlayers since there is a largerdifference between the two temperatures.

Damping loss factor was measured on all the interlayers, as shown inTable 3. For the 5 mils core layers, at all plasticizer levels, dampingloss factor is similar to that of the control samples at all threetemperatures. For the 10 mils core layers, at all plasticizer levels,damping loss factor is significantly higher at 10° C. and 20° C. andslightly lower at 30° C. When there is a larger difference in residualhydroxyl content between the two resins, the sound insulation can beimproved at lower temperatures by increasing the core layer thickness.

TABLE 4 Core layer Glass transition Observed Core First Secondtemperatures of layer glass Ratio resin resin Average individualtransition Damping of residual residual residual Plas- plasticizedtemperatures loss factor Inter- Core PVB First/ hydroxyl hydroxylhydroxyl ticizer thick- resins (° C.) (° C.) (η) at tem- layer layerresin(s) Second content content content content ness First Second FirstSecond perature (° C.) No no. Used resin (wt. %) (wt. %) (wt. %) (phr)(mil) T_(g1) T_(g2) T_(g1) T_(g2) 10 20 30 CI-2 CL-1 A — 10.5 — 10.5 7510 −2 — −2.5 — 0.28 0.45 0.26 DI-5 DL-1 B, E 50/50  9.6 11.5 10.5 75 10−4.5 1.9 0.2 — 0.42 0.50 0.25 DI-6 DL-2 B, E 50/50  9.6 11.5 10.5 70 10−2.2 3.7 1.4 — 0.37 0.54 0.25 DI-7 DL-3 B, E 50/50  9.6 11.5 10.5 65 100.4 5.8 3.4 — 0.31 0.56 0.28 DI-21 DL-11 B, C 75/25  9.6 13 10.5 75 10−4.5 4.9 −3.7 — 0.38 0.49 0.27 DI-22 DL-12 B, C 75/25  9.6 13 10.5 70 10−2.2 6.7 −2.3 — 0.33 0.54 0.29 DI-23 DL-13 B, C 75/25  9.6 13 10.5 65 100.4 8.7 0.4 — — — — DI-13 DL-5 B, C 50/50  9.6 13 11.3 75 10 −4.5 4.9 −1— 0.34 0.49 0.28 DI-14 DL-6 B, C 50/50  9.6 13 11.3 70 10 −2.2 6.7 1 —0.26 0.55 0.40 DI-15 DL-7 B, C 50/50  9.6 13 11.3 65 10 0.4 8.7 3.8 —0.21 0.55 0.41 DI-24 DL-14 B, D 75/25  9.6 16.3 11.3 75 10 −4.5 9.5 −5.024 0.33 0.44 0.32 DI-25 DL-15 B, D 75/25  9.6 16.3 11.3 70 10 −2.2 10.7−2.7 25.8 0.27 0.42 0.31 DI-26 DL-16 B, D 75/25  9.6 16.3 11.3 65 10 0.412.3 0 27.1 0.26 0.46 0.33

Table 4 compares interlayers having comparative core layers with aresidual hydroxyl content of about 10.5 wt. % with disclosed core layerscomprising two resins with an average residual hydroxyl content of about10.5 wt. % and 11.3 wt. %. Compare disclosed interlayers DI-5, DI-6 andDI-7 to DI-21, DI-22 and DI-23, which have the same average residualhydroxyl contents. The average residual hydroxyl content of about 10.5wt. % was obtained by blending two resins (Resin-B at 9.6 wt. % andResin-E at 11.5 wt. % residual hydroxyl content, respectively, with adelta residual hydroxyl content of 1.9 wt. %) at a ratio 50:50. Thissame average residual hydroxyl content of about 10.5 wt. % was also beobtained by blending two different resins (Resin-B at 9.6 wt. % andResin-C at 13 wt. % residual hydroxyl content, respectively, with adelta residual hydroxyl content of 3.4 wt. %) at a ratio of 75:25.Compare disclosed interlayers DI-13, DI-14 and DI-15 to DI-24, DI-25 andDI-26, which have the same average residual hydroxyl contents. Theaverage residual hydroxyl content of about 11.3 wt. % was obtained byblending two resins (Resin-B at 9.6 wt. % and Resin-C at 13 wt. %residual hydroxyl content, respectively, with a delta residual hydroxylcontent of 3.4 wt. %) at a ratio 50:50. This same average residualhydroxyl content of about 11.3 wt. % was also be obtained by blendingtwo different resins (Resin-B at 9.6 wt. % and Resin-D at 16.3 wt. %residual hydroxyl content, respectively, with a delta residual hydroxylcontent of 6.7 wt. %) at a ratio of 75:25.

Core layers were formed at a thickness of 10 mils and at varyingplasticizer levels of from 65 phr to 75 phr. Glass transitiontemperatures for the individual plasticized resins are shown, as well asthe glass transition temperature(s) of the core layer. In some cases,since the individual glass transition temperatures do not differ by alarge amount or the glass transition peak of the second plasticizedresin is weak due to the presence of the resin at a smaller amount, onlyone glass transition temperature is measured on the core layer, which isbetween the two individual glass transition temperatures.

At the average residual hydroxyl content of about 10.5 wt. %, when thedifference in residual hydroxyl content between the first and secondresin is smaller (1.9 wt. %), damping loss factor is improved at 10 and20° C. for 5 mils core layer (DI-5 to DI-7); increasing the differencefrom 1.9% to 3.4%, e.g., increasing the residual hydroxyl of the secondresin from 11.5% to 13%, results in a more balanced increase in dampingloss factor at all three temperature (DI-21 to DI-22). At the averageresidual hydroxyl content of about 11.3 wt. % and the difference inresidual hydroxyl content between the first and second resin of 3.4 wt.%, damping loss factor is improved at 20 and 30° C. (DI-13 to DI-15);increasing the difference from 3.4% to 6.7%, e.g., increasing theresidual hydroxyl of the second resin from 13% to 16.3%, results in anincrease in damping loss factor at 30° C. (DI-25 and DI-26) atplasticizer levels of 65 and 70 and a more balanced increase at allthree temperatures (DI-24).

This is clearly illustrated by comparing the control interlayer, CI-2,where the damping loss factor is maximized at 20° C. (and it decreasesat both 10° C. and 30° C.) with the disclosed interlayers, such as DI-5,DI-6, DI-7, DI-21 and DI-22, where the damping loss factor is alsomaximized at 20° C. but also increases at 10° C. and remains essentiallyunchanged compared to the control interlayer at 30° C. Comparing thecontrol interlayer, CI-2, with the disclosed interlayers DI-13, DI-14,DI-15, DI-24, DI-25 and DI-26, the damping loss factor is also maximizedat 20° C. but also increases at 30° C. and drops slightly in some casesand remains essentially unchanged in others compared to the controlinterlayer at 10° C. This shows that interlayers having two resinshaving different hydroxyl contents in different ratios can be combinedto provide better sound insulation over a broader range of temperatures.

In conclusion, the multilayered interlayers with core layers describedherein have numerous advantages over conventional multilayeredinterlayers previously utilized in the art. In general, in comparison tomultilayered interlayers previously utilized in the art, themultilayered interlayers comprising core layers as described herein,having two (or more) different resins having different hydroxyl contentsand glass transition temperatures, have an improved sound insulationperformance and broaden the temperature range at which the interlayersperform. Other advantages will be readily apparent to those skilled inthe art.

While the invention has been disclosed in conjunction with a descriptionof certain embodiments, including those that are currently believed tobe the preferred embodiments, the detailed description is intended to beillustrative and should not be understood to limit the scope of thepresent disclosure. As would be understood by one of ordinary skill inthe art, embodiments other than those described in detail herein areencompassed by the present invention. Modifications and variations ofthe described embodiments may be made without departing from the spiritand scope of the invention.

It will further be understood that any of the ranges, values, orcharacteristics given for any single component of the present disclosurecan be used interchangeably with any ranges, values or characteristicsgiven for any of the other components of the disclosure, wherecompatible, to form an embodiment having defined values for each of thecomponents, as given herein throughout. For example, an interlayer canbe formed comprising poly(vinyl butyral) having a residual hydroxylcontent in any of the ranges given in addition to comprising aplasticizers in any of the ranges given to form many permutations thatare within the scope of the present disclosure, but that would becumbersome to list. Further, ranges provided for a genus or a category,such as phthalates or benzoates, can also be applied to species withinthe genus or members of the category, such as dioctyl terephthalate,unless otherwise noted.

The invention claimed is:
 1. A polymer interlayer having improved soundinsulation, the polymer interlayer comprising: at least one soft layerwherein the soft layer comprises a blend of two or more poly(vinylbutyral) resins comprising: a first poly(vinyl butyral) resin having afirst residual hydroxyl content and a first glass transition temperature(T_(g)); a second poly(vinyl butyral) resin having a second residualhydroxyl content and a second glass transition temperature (T_(g)),wherein the difference between the first residual hydroxyl content andthe second residual hydroxyl content is at least 1.0 weight percent;wherein the difference between the first glass transition temperature(T_(g)) and the second glass transition temperature (T_(g)) is at least1.5° C.; and a plasticizer, wherein the first poly(vinyl butyral) resin,the second poly(vinyl butyral) resin and the plasticizer are mixed andmelt-extruded to form the at least one soft layer; at least one stifferlayer comprising a third poly(vinyl butyral) resin having a thirdresidual hydroxyl content; and a plasticizer, wherein the polymerinterlayer has a damping loss factor (η) (as measured by MechanicalImpedance Measurement according to ISO 16940) of at least about 0.16measured at two or more different temperatures selected from 10° C., 20°C. and 30° C.
 2. The polymer interlayer of claim 1, wherein the secondpoly(vinyl butyral) resin is present in an amount of from about 5 weightpercent to about 50 weight percent.
 3. The polymer interlayer of claim1, wherein the second poly(vinyl butyral) resin is present in an amountof from about 25 weight percent to about 50 weight percent.
 4. Thepolymer interlayer of claim 1, wherein each plasticized resin in thesoft layer of the polymer interlayer has a glass transition temperature(T_(g)) less than 20.0° C.
 5. The polymer interlayer of claim 1, whereinthe residual hydroxyl content of the third poly(vinyl butyral) resin isthe same as the residual hydroxyl content of the first poly(vinylbutyral) resin or the second poly(vinyl butyral) resin.
 6. The polymerinterlayer of claim 1, wherein the difference between the first residualhydroxyl content and the second residual hydroxyl content is at least2.0 weight percent.
 7. The polymer interlayer of claim 1, wherein thedifference between the first residual hydroxyl content and the secondresidual hydroxyl content is at least 3.0 weight percent.
 8. The polymerinterlayer of claim 1, wherein the difference between the glasstransition temperatures (T_(g)) of the first poly(vinyl butyral) resinand the second poly(vinyl butyral) resin is at least 3.0° C.
 9. Apolymer interlayer having improved sound insulation, the polymerinterlayer comprising: at least one soft layer wherein the soft layercomprises a blend of two or more poly(vinyl butyral) resins comprising:a first poly(vinyl butyral) resin having a first residual hydroxylcontent and a first glass transition temperature (T_(g)); a secondpoly(vinyl butyral) resin having a second residual hydroxyl content anda second glass transition temperature (T_(g)), wherein the differencebetween the first residual hydroxyl content and the second residualhydroxyl content is at least 1.0 weight percent; wherein the differencebetween the first glass transition temperature (T_(g)) and the secondglass transition temperature (T_(g)) is at least 1.5° C.; and aplasticizer, wherein the first poly(vinyl butyral) resin, the secondpoly(vinyl butyral) resin and the plasticizer are mixed andmelt-extruded to form the at least one soft layer; at least one stifferlayer comprising a third poly(vinyl butyral) resin having a thirdresidual hydroxyl content; and a plasticizer, wherein the polymerinterlayer has a damping loss factor (η) (as measured by MechanicalImpedance Measurement according to ISO 16940) of at least about 0.16measured at two or more different temperatures selected from 10° C., 20°C. and 30° C., and wherein the second poly(vinyl butyral) resin ispresent in an amount of from about 5 weight percent to about 50 weightpercent.
 10. The polymer interlayer of claim 9, wherein each plasticizedresin in the soft layer of the polymer interlayer has a glass transitiontemperature (T_(g)) less than 20.0° C.
 11. The polymer interlayer ofclaim 9, wherein the residual hydroxyl content of the third poly(vinylbutyral) resin is the same as the residual hydroxyl content of the firstpoly(vinyl butyral) resin or the second poly(vinyl butyral) resin. 12.The polymer interlayer of claim 9, wherein the difference between thefirst residual hydroxyl content and the second residual hydroxyl contentis at least 2.0 weight percent.
 13. The polymer interlayer of claim 9,wherein the difference between the first residual hydroxyl content andthe second residual hydroxyl content is at least 3.0 weight percent. 14.The polymer interlayer of claim 9, wherein difference between the glasstransition temperatures (T_(g)) of the first poly(vinyl butyral) resinand the second poly(vinyl butyral) resin is at least 3.0° C.
 15. Apolymer interlayer having improved sound insulation, the polymerinterlayer comprising: at least one soft layer wherein the soft layercomprises a blend of two or more poly(vinyl butyral) resins comprising:a first poly(vinyl butyral) resin having a first residual hydroxylcontent and a first glass transition temperature (T_(g)); a secondpoly(vinyl butyral) resin having a second residual hydroxyl content anda second glass transition temperature (T_(g)), wherein the differencebetween the first residual hydroxyl content and the second residualhydroxyl content is at least 1.0 weight percent, wherein the differencebetween the first glass transition temperature (T_(g)) and the secondglass transition temperature (T_(g)) is at least 1.5° C.; and aplasticizer, wherein the first poly(vinyl butyral) resin, the secondpoly(vinyl butyral) resin and the plasticizer are mixed andmelt-extruded to form the at least one soft layer; at least one stifferlayer comprising a third poly(vinyl butyral) resin having a thirdresidual hydroxyl content; and a plasticizer, wherein each plasticizedresin in the soft layer of the polymer interlayer has a glass transitiontemperature (T_(g)) less than 20.0° C.
 16. The polymer interlayer ofclaim 15, wherein the second poly(vinyl butyral) resin is present in anamount of from about 5 weight percent to about 50 weight percent. 17.The polymer interlayer of claim 15, wherein the second poly(vinylbutyral) resin is present in an amount of from about 25 weight percentto about 50 weight percent.
 18. The polymer interlayer of claim 15,wherein the difference between the glass transition temperatures (T_(g))of the first poly(vinyl butyral) resin and the second poly(vinylbutyral) resin is at least 3.0° C.
 19. The polymer interlayer of claim15, wherein the difference between the first residual hydroxyl contentand the second residual hydroxyl content is at least 2.0 weight percent.20. The polymer interlayer of claim 15, wherein the difference betweenthe first residual hydroxyl content and the second residual hydroxylcontent is at least 3.0 weight percent.